KR102386784B1 - Soft magnetic flake composite and method of preparing the same - Google Patents

Abstract

The present application relates to a soft magnetic flake composite, a method for manufacturing the same, and a device comprising the same.

Description

Soft magnetic flake composite and manufacturing method thereof

The present application relates to a soft magnetic flake composite, a method for manufacturing the same, and a device comprising the same.

In complex communication systems such as wireless autonomous vehicles that use electromagnetic (EM) wave absorbing films, the need for specific frequency blocking of electromagnetic (EM) waves becomes increasingly important. Increasing safety requirements require films to operate with very precise and precise frequency selectivity, while commercial specifications require very thin thicknesses.

, 여기서 ε은 전기 유전율, μ는 자기 투자율)을 나타내어 상기 필름의 두께가 입사하는 EM 파에 대하여 효과적으로 더 크게 나타나야 한다. 흡수를 극대화하려면, 임피던스는 필름과 주변(surrounding)사이에서 일치되어 반사로 인한 전력 손실을 방지해야 한다. 굴절률을 높이기 위해 높은 ε의 유전체 필름을 선택할 수 있지만, 이는 주변과의 높은 특성 임피던스 (η =

) 불일치를 야기한다.Due to the need to prevent electronic malfunction due to stray EM signals of specific frequencies in wireless autonomous systems, interest in EM wavelength absorbing films with narrow absorption bandwidths is increasing. For an absorber film to operate at a precise and precise frequency, variations in film thickness must be minimized, as variations in the thickness of the film can shift the absorption response away from the target frequency. In addition, the demand for films thinner than a quarter wavelength has increased due to efforts to miniaturize electrical components. In order for the film to be thinner, the film has a large refractive index (n =

, where ε is electric permittivity, μ is magnetic permeability), so that the thickness of the film should be effectively larger with respect to the incident EM wave. To maximize absorption, the impedance must be matched between the film and the surrounding to prevent power loss due to reflection. A dielectric film with high ε can be selected to increase the refractive index, but this results in a high characteristic impedance with the surroundings (η =

) causes inconsistencies.

) 지수 및 상기 복합체의 특성 임피던스 (characteristic impedance,

)는, 자기 및 유전체 함량의 균형을 맞춤으로써, 최적화할 수 있다. 일단 EM 파가 상기 자기유전체 매체에 들어가면, 결합된 자기 및 전기 손실 메커니즘이 효과적으로 파동을 분산시킬 수 있다.A solution to this problem can be found in magnetodielectric composites, which can employ both high permeability and permittivity in nano- or micron-sized magnetic and dielectric units. refractive index (

) index and the characteristic impedance of the complex (characteristic impedance,

) can be optimized by balancing the magnetic and dielectric contents. Once the EM wave enters the magnetoelectric medium, the combined magnetic and electrical loss mechanism can effectively disperse the wave.

Even if the characteristic impedance matching is not good, a remarkably high absorption at a specific frequency is possible by adjusting the wave impedance (Z _in ) with the film thickness. Wave impedance matching occurs at the thickness specified by the quarter-wavelength condition (ie, λ/4n), meaning that the absorption frequency can be controlled by the thickness. This is useful for tuning the absorption frequency, but can be disadvantageous for high-precision EM applications, as small variations in thickness can shift the absorption frequency away from the target. Films that strongly absorb only in their intrinsic thickness and frequency may be more suitable, which can be realized by incorporating each of magnetic and dielectric components that exhibit large permeability and permittivity.

As a high dielectric constant, BaTiO ₃ has been shown to exhibit excellent microwave absorption properties in the form of various nanostructures. According to the study, the tetragonal BaTiO ₃ domain wall movement under the application of EM excitation can determine the complex permittivity, which can be controlled by the oxygen vacancy concentration.

As a magnetic material having high magnetic permeability at high frequency, an iron alloy including Si or Al is being studied. In particular, FeSiAl has been widely used in commercial EM interference shielding and absorbing films due to its low magnetocrystalline anisotropy, low coercivity, and high temperature stability.

Various strategies have been implemented to increase the permeability. However, eddy currents, which are currents induced from an applied magnetic field, generally limit the permeability. This current can be reduced by increasing the resistivity of the material or by breaking the current path between the particles. To this end, it has been found that the permeability can be increased by flattening the spherical particles in the form of flakes. Coating the particles with an insulator, which can be made of organic or inorganic materials, has also been demonstrated to prevent eddy current build-up in electrically contacting particles. However, the manufacture of magnetic particles involves complex chemical processes that are challenging for practical implementation.

Republic of Korea Patent Publication No. 10-1572459.

An object of the present application is to provide a soft magnetic flake composite, a method for manufacturing the same, and a device including the same.

However, the problems to be solved by the present application are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A first aspect of the present disclosure provides a soft magnetic flake composite comprising: a soft magnetic flake and a dielectric particle:

A second aspect of the present disclosure includes: (a) pulverizing a dielectric particle precursor mixture and then heat-treating to prepare dielectric particles; and (b) performing a heat press on a mixture prepared by mixing the soft magnetic flakes and the dielectric particles with a polymer resin to obtain a soft magnetic flake composite. A method for producing a soft magnetic flake composite according to the first aspect, to provide.

A third aspect of the present disclosure provides a device comprising the soft magnetic flake composite according to the first aspect.

In the embodiments of the present application, by including the dielectric particles in the soft magnetic flake composite, one or more selected from dielectric constant, magnetic permeability, saturation magnetic flux density, and effective refractive index of the soft magnetic flake may be improved. Here, since the dielectric particles are included between the soft magnetic flakes, the loss of eddy current is reduced, the saturation magnetic flux density is improved due to physical stress and deformation occurring on the surface of the soft magnetic flakes, and the magnetic permeability can also be improved.

In the embodiments of the present application, when the soft magnetic flakes are arranged in a stacked structure, the eddy current occurring between the soft magnetic flakes may cancel the magnetic properties, but the dielectric particles are formed between the soft magnetic flakes of the stacked structure. When added, the eddy current occurring between the soft magnetic flakes is canceled and magnetic properties can be maximized through this. In order to suppress the loss of magnetic properties due to eddy current, conventional studies have mixed materials such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ with FeSiAl through a wet process. There was a problem in that the existing magnetic properties of FeSiAl could not be maintained. However, the soft magnetic flake composite of the present application is significant in that each property is rather improved while maintaining the intrinsic properties of the material included in the composite by using a dry process ( FIGS. 3E and 3F ).

In the embodiments of the present application, by adding and heat pressing the dielectric particles between the soft magnetic flakes, a physical stress is applied to the surface of the soft magnetic flakes by the dielectric particles, and the atomic structure of the soft magnetic flakes is deformed. As this appears, the saturation magnetic flux density may be improved.

In the embodiments of the present disclosure, the dielectric constant of the soft magnetic flake composite may be improved by adding the dielectric particles between the soft magnetic flakes.

In the embodiments of the present application, the soft magnetic flake composite may absorb microwaves. The soft magnetic flake composite according to the embodiments of the present application exhibits more improved magnetic permeability and dielectric constant, and since the effective refractive index is a product of the real part of the magnetic permeability and the dielectric constant, the effective refractive index may also be improved. Such improvement of the effective refractive index can reduce the thickness of the absorbent required when the soft magnetic flake composite is used as a microwave absorber. That is, when the microwave absorbent in the form of a film is used, as the effective refractive index increases, the thickness of the absorber film having the maximum microwave absorption capacity may be reduced. Therefore, when the soft magnetic flake composite according to an embodiment of the present application is used as a microwave absorbing film material, microwave absorption is possible at a thinner thickness than the conventional soft magnetic flake composite.

In the embodiments of the present application, the wavelength (f) at which the microwave absorption is maximized by the point at which the return loss value that can be confirmed through the reflection loss map is the lowest, the thickness (T) of the film, and the wavelength versus the thickness (λ:T ) can be obtained, and the thickness of the film corresponding to the point at which the microwave absorption rate measured using the soft magnetic flake composite according to the embodiments of the present application is maximum is about twice as thin as that of the conventional film. can

In the embodiments of the present application, the present inventors demonstrate the simultaneous increase of the magnetic permeability and the dielectric constant of the soft magnetic composite by simply mixing the ferroelectric BaTiO ₃ fine particles into the soft magnetic FeSiAl flake composites. Adding BaTiO ₃ particles improves the permeability of the composite through two pathways. First, the BaTiO ₃ particles separate the FeSiAl flakes in contact, reducing the eddy current loss and increasing the composite permeability. Second, the added volume of BaTiO ₃ particles puts more stress on the FeSiAl flakes when hot pressed into a mold of fixed dimensions, which increases the saturation magnetization, which improves the high-frequency permeability. At the same time, the ferroelectric properties of BaTiO ₃ particles increase the composite permittivity, which can be further controlled by adjusting the oxygen deficiency content. At various mass ratios of FeSiAl and BaTiO ₃ , the composite exhibits improved magnetic permeability and dielectric constant, resulting in a refractive index improvement of about 25% to about 144%, and a decrease in film thickness, while at the same time exhibiting a return loss of up to 60 dB below 1 GHz. shows that it occurs. Through wave impedance matching, the metal dielectric complex can exhibit perfect absorption with an inherent thickness that is 10 times thinner than a quarter wavelength in free space.

= 1 (적색) 및

= 0 (청색) 조건은 파장 임피던스가 공기와 일치함을 나타낸다. 또한, 도 8c는 두께 7.6 mm에서의 반사 손실 및 복합 파동 임피던스 스펙트라 [(a) 및 (b)의 점선에서) 40 wt%FeSiAl- 30 wt%DBTO 입자 복합체 (왼쪽) 및 이에 상응하는 FeSiAl 레퍼런스 샘플(오른쪽 패널)]를 나타낸 것이다.
도 9는 각각 (a) x =10 wt%, (b) 30 wt%, (c) 40 wt%, 및 (d) 60 wt%에서, (70 wt%-x) FeSiAl - xDBTO 입자 복합체 (왼쪽 패널), (70 wt%-x) FeSiAl - xWBTO입자 복합체 (가운데 패널) (70 wt%-x) FeSiAl 레퍼런스 (오른쪽 패널)에 대한 두께 및 주파수의 함수로 계산된 반사손실을 나타낸 것으로서, 삽입된 수치는 복합체의 굴절률로부터 계산된 λ/4n 두께를 나타낸다. 여기서, 각각의 표는 반사 손실 맵(map)으로부터 얻은 샘플의 목표 주파수 및 두께, 그리고 상응하는 두께 대 파장을 나타내는 것으로서, x = 40 wt% 및 60 wt% 인 FeSiAl 레퍼런스의 경우, 목표 주파수가 1 MHz 내지 1,000 MHz 범위를 벗어나므로, 파장과 두께는 범위로서 표시되었다.
도 10a는 40 wt% FeSiAl - 30 wt% DBTO입자 복합체의 두께 및 파장의 함수로 계산된 반사 손실(위) 및 복합 파동 임피던스 (중간 및 아래)를 나타낸 것이고, 도 10b는 5 mm, 10 mm 및 15 mm 두께에서, 40 wt% FeSiAl-30 wt% DBTO 입자 복합체의 반사 손실 및 복합 파동 임피던스 프로필을 나타낸 것이다.
도 11a는 FeSiAl 60wt% 복합체와 FeSiAl 60 wt% + TiO₂ 10 wt% 복합체의 포화 자속밀도를 비교한 결과이며, 도 11b는 FeSiAl 40 wt% 복합체와 FeSiAl 40 wt% + TiO₂ 30 wt% 복합체의 포화 자속밀도를 비교한 결과이다.1 is a schematic diagram of a soft magnetic flake composite and its effects according to embodiments of the present application.
Figure 2 relates to the properties of FeSiAl flakes and DBTO particles, Figure 2a is an SEM image of FeSiAl flake powder (inset is a photograph of FeSiAl powder), Figure 2b is an XRD spectra of 40 wt% FeSiAl in polyurethane ( before heat press: black, after: red). In addition, FIG. 2c is an SEM image of DBTO particles (inset is a photograph of DBTO powder), FIG. 2d is an XRD spectrum of DBTO particles, and FIG. 2e is a manufacturing process of a soft magnetic flake composite according to an embodiment of the present application. it is a schematic diagram
3a is XRD spectra and the ratio of (200) and (110) peak intensities of 60 wt% FeSiAl and 40 wt% FeSiAl reference samples subjected to heat press treatment are shown, and Figure 3b is 60 wt% FeSiAl and 40 wt% before heat press treatment The XRD spectra of the % FeSiAl reference sample and the ratio of the (200) peak intensity to the (110) peak intensity are shown.
4a to 4d are respectively (a) 60 wt% FeSiAl reference, (b) 60 wt% FeSiAl - 10 wt% DBTO particle composite, (c) 40 wt% FeSiAl reference and (d) according to an embodiment of the present application. It is a SEM image of a cross-section of a 40 wt% FeSiAl - 30 wt% DBTO particle composite sample, and FIGS. 4e and 4f show an eddy current schematic diagram of FeSiAl flakes for (e) reference and (f) FeSiAl-DBTO particle composites, respectively. .
Figure 5a shows the magnetic hysteresis of 60 wt% FeSiAl-10 wt% DBTO particle composite (solid red line), 60 wt% FeSiAl-10 wt% WBTO particle composite (light red solid line), and 60 wt% FeSiAl reference sample (black dashed line). A loop is shown, and FIG. 5b is a 40 wt% FeSiAl-30 wt% DBTO particle composite (solid blue line), 40 wt% FeSiAl-30 wt% WBTO particle composite (light blue solid line), and a 40 wt% FeSiAl reference sample (black line). The dotted line) shows the magnetic hysteresis loop.
6a and 6b show the composite permeability and the composite permittivity measured as a function of frequency, respectively, and the actual and expected values are indicated by solid and dotted lines, respectively [(70 wt%- x )FeSiAl- x DBTO particle composite, where x = 10 wt % (red), 30 wt % (blue), 40 wt % (green), and 60 wt % (purple), and the corresponding FeSiAl reference sample (black), (70 wt % - x ) composite permittivity of FeSiAl- x WBTO particle composites (each in light colors)].
7 is the refractive index as a function of frequency, respectively [(70 wt%- x )FeSiAl- x DBTO particle composite (dark color), (70 wt%- x )FeSiAl- x WBTO particle composite (light color), where x = 10 wt% (red), 30 wt% (blue), 40 wt% (green), and 60 wt% (purple), and the corresponding FeSiAl reference sample (black)].
8a and 8b show (a) return loss and (b) complex wave impedance matching conditions calculated as a function of thickness and frequency, respectively [40 wt% FeSiAl-30 wt% DBTO particle composite (left) and the corresponding FeSiAl reference composite) (right)] as

= 1 (red) and

The condition = 0 (blue) indicates that the wavelength impedance matches air. In addition, Fig. 8c shows the return loss and complex wave impedance spectra at a thickness of 7.6 mm [in the dashed lines in (a) and (b)) of a 40 wt%FeSiAl-30 wt%DBTO particle composite (left) and the corresponding FeSiAl reference sample. (right panel)].
9 shows (70 wt% -x ) FeSiAl- x DBTO particle composites at (a) x =10 wt%, (b) 30 wt%, (c) 40 wt%, and (d) 60 wt%, respectively; Left panel), (70 wt%- x ) FeSiAl- x WBTO particle composite (middle panel) (70 wt%- x ) FeSiAl reference (right panel) as a function of thickness and frequency for the calculated return loss, The inset represents the λ/4n thickness calculated from the refractive index of the composite. Here, each table shows the target frequency and thickness of the sample obtained from the return loss map, and the corresponding thickness versus wavelength, where for the FeSiAl reference with x = 40 wt% and 60 wt%, the target frequency is 1 Outside the MHz to 1,000 MHz range, wavelengths and thicknesses are expressed as ranges.
Figure 10a shows the calculated return loss (top) and composite wave impedance (middle and bottom) as a function of thickness and wavelength of a 40 wt% FeSiAl-30 wt% DBTO particle composite, and Figure 10b shows 5 mm, 10 mm and The return loss and composite wave impedance profiles of 40 wt% FeSiAl-30 wt% DBTO particle composites at 15 mm thickness are shown.
Figure 11a is the result of comparing the saturation magnetic flux density of the FeSiAl 60wt% composite and FeSiAl 60wt% + TiO ₂ 10wt% composite, Figure 11b is the FeSiAl 40wt% composite and FeSiAl 40wt% + TiO ₂ 30wt% composite This is the result of comparing the saturation magnetic flux density.

Hereinafter, with reference to the accompanying drawings, embodiments and examples of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily carry out. However, the present application may be embodied in several different forms and is not limited to the embodiments and examples described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout this specification, when a part is "connected" with another part, this includes not only the case where it is "directly connected" but also the case where it is "electrically connected" with another element interposed therebetween. do.

Throughout this specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

Throughout this specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

As used herein, the terms "about," "substantially," and the like are used in a sense at or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and to aid in the understanding of the present application. It is used to prevent an unconscionable infringer from using the mentioned disclosure in an unreasonable way.

As used throughout this specification, the term “step of doing” or “step of” does not mean “step for”.

Throughout this specification, the term "combination(s) of these" included in the expression of the Markush form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Markush form, It means to include one or more selected from the group consisting of the above components.

Throughout this specification, reference to “A and/or B” means “A or B, or A and B”.

Hereinafter, embodiments of the present application have been described in detail, but the present application may not be limited thereto.

A first aspect of the present disclosure provides a soft magnetic flake composite comprising a soft magnetic flake and a dielectric particle.

In one embodiment of the present application, the soft magnetic flakes are arranged in a stacked structure, and dielectric particles may be included between the soft magnetic flakes, but may not be limited thereto.

In one embodiment of the present application, the soft magnetic flakes include at least one selected from FeAlSi, Fe-Si alloy, Ni-Fe alloy, and MO _x ·Fe ₂ O ₃ , wherein M is Ni, Mn or Zn, and may be 0≤x<3, but may not be limited thereto. In one embodiment of the present application, the soft magnetic flakes may be FeAlSi. Here, the soft magnetic flake is a material having high magnetic permeability and saturation magnetic flux density in the microwave band, and is mainly used for electromagnetic wave absorption.

In one embodiment of the present application, the dielectric particles are BaTiO _3-y , TiO _2-z , Si, Ge, Sn, SiC, S ₈ , Se, Te, BN, BP, BAs, ZnO, ZnSe, ZnS, ZnTe , CuCl, Cu ₂ S, PbSe, PbS, ObTe, SnS, SnS ₂ , SnTe, B ₁₂ As ₂ , AlN, AlP, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, CdS, CdSe, CdTe, InGaP , InGaN, InN, InP, InAs, InSb, PbSeTe, Tl ₂ SnTe ₅ , Tl ₂ GeTe ₅ , Bi ₂ Te ₃ , Cd ₃ P ₂ , Cd ₃ As ₂ , Cd ₃ Sb ₂ , ZnsP ₂ , Zn ₃ As ₂ , Zn ₃ Sb ₂ , Cu ₂ O, CuO, UO ₂ , UO ₃ , Bi ₂ O ₃ , SnO ₂ , SrTiO ₃ , LiNbO ₃ , La ₂ CuO ₄ , PbI ₂ , MoS ₂ , VO ₂ , V ₂ O ₃ , GaSe, Bi ₂ S ₃ , NiO, CuInSe ₂ , Ag ₂ S, FeS ₂ , Cu ₂ ZnSnS ₄ , CuZnSbS, Cu ₂ SnS ₃ , Si _1-x Ge _x , Si _1-x Sn _x , AlxGa _1-x As, InxGa _1-x As, In _x Ga _1-x P, Al _x In _1-x As, Al _x In _1-x Sb, GaAsN, GaAsP, GaAsSb, AlGaN, AlGaP, InGaN, InAsSb, InGaSb, AlGaInP, AlGaAsP, IGaAsP, InGaAsSb, InAsSbP, AlInAsP, AlGaAsN, InGaAsN, InAsAsN, GaAsSbN, GaInNAsSb, GaInAsSbP, CdZnTe, HgCdTe, HgZnTe, HgZnSe, and Cu(In,Ga)Se ₂ containing one or more materials selected from 0 ≤y<3, and may be 0≤z<2, but may not be limited thereto. Here, the dielectric particle is a nonmagnetic material exhibiting a high dielectric constant in the GHz band, and is a material having no magnetic properties and no magnetic permeability.

In one embodiment of the present application, the dielectric particles may be oxygen-deficient in the axial direction, but may not be limited thereto. In one embodiment of the present application, the dielectric particles are axially deoxygenated BaTiO ₃ (y=0; hereinafter also referred to as “WBTO”) or axially oxygenated BaTiO _3-y (0<y<3; Hereinafter, also referred to as "DBTO"). In one embodiment of the present application, the dielectric particles may be non-axially oxygen-deficient TiO ₂ (z=0) or axially oxygen-deficient TiO _2-z (0<z<2).

In one embodiment of the present application, the dielectric particles may be BaTiO ₂ , BaTiO ₃ , or TiO ₂ .

In one embodiment of the present application, the weight ratio of the soft magnetic flakes and the dielectric particles may be from about 8:1 to about 1:8, but may not be limited thereto. For example, the soft magnetic flake and the dielectric particle may have a weight ratio of about 8:1 to about 1:8, about 8:1 to about 1:6, about 8:1 to about 1:4, about 8:1 to about 3: 4, about 8:1 to about 1: 2, about 8:1 to about 1:1, about 8:1 to about 4:3, about 8:1 to about 2: 1, about 8:1 to about 4:1, about 8:1 to about 6:1, about 6:1 to about 1:8, about 6:1 to about 1:6, about 6:1 to about 1:4, about 6:1 to about 3: 4, about 6: 1 to about 1: 2, about 6: 1 to about 1:1, about 6: 1 to about 4: 3, about 6: 1 to about 2: 1, about 6: 1 to about 4:1, about 4:1 to about 1:8, about 4:1 to about 1:6, about 4:1 to about 1:4, about 4:1 to about 3:4, about 4:1 to about 1 : 2, about 4 : 1 to about 1 : 1, about 4 : 1 to about 4: 3, about 4 : 1 to about 2 : 1, about 2 : 1 to about 1 : 8, about 2 : 1 to about 1 : 6, about 2 : 1 to about 1 : 4, about 2 : 1 to about 3 : 4, about 2 : 1 to about 1 : 2, about 2 : 1 to about 1:1, about 2 : 1 to about 4:3, about 4:3 to about 1:8, about 4:3 to about 1:6, about 4:3 to about 1:4, about 4:3 to about 3:4, about 4:3 to about 1:2, about 4:3 to about 1:1, about 1:1 to about 1:8, about 1:1 to about 1:6, about 1:1 to about 1:4, about 1:1 to about 3: 4, about 1:1 to about 1: 2, about 1: 2 to about 1: 8, about 1: 2 to about 1: 6, about 1: 2 to about 1: 4, about 1: 2 to about 3: 4, about 3: 4 to about 1: 8, about 3: 4 to about 1: 6, about 3: 4 to about 1: 4, about 1: 4 to about 1: 8, about 1: 4 to about 1: 6, or about 1: 6 to about 1: 8, but may not be limited thereto. In one embodiment of the present application, the weight ratio of the soft magnetic flakes and the dielectric particles may be about 6:1, about 4:3, about 3:4, or about 1:6.

In one embodiment of the present application, by including the dielectric particles in the soft magnetic flake composite, one or more selected from dielectric constant, magnetic permeability, saturation magnetic flux density, and effective refractive index of the soft magnetic flake may be improved. Here, since the dielectric particles are included between the soft magnetic flakes, the loss of eddy current is reduced, the saturation magnetic flux density is improved due to physical stress and deformation occurring on the surface of the soft magnetic flakes, and the magnetic permeability can also be improved (Fig. One).

Specifically, when the soft magnetic flakes are arranged in a stacked structure, eddy currents occurring between the soft magnetic flakes may cancel out the magnetic properties. When the dielectric particles are added between the soft magnetic flakes of the laminated structure, eddy currents occurring between the soft magnetic flakes can be offset and magnetic properties can be maximized. In order to suppress the loss of magnetic properties due to eddy current, conventional studies have mixed materials such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ with FeSiAl through a wet process. There was a problem in that the existing magnetic properties of FeSiAl could not be maintained. However, the soft magnetic flake composite of the present application is significant in that each property is rather improved while maintaining the intrinsic properties of the material included in the composite by using a dry process ( FIGS. 3E and 3F ).

In addition, by adding the dielectric particles between the soft magnetic flakes and heat pressing, physical stress is applied to the surface of the soft magnetic flakes by the dielectric particles, and the atomic structure deformation of the soft magnetic flakes appears, resulting in saturation magnetic flux. The density can be improved ( FIG. 2E ).

In addition, by adding the dielectric particles between the soft magnetic flakes, the dielectric constant of the soft magnetic flake composite may be improved.

In one embodiment of the present application, the soft magnetic flake composite may absorb microwaves. The soft magnetic flake composite according to the exemplary embodiment of the present application exhibits more improved magnetic permeability and dielectric constant, and since the effective refractive index is a product of the real part of the magnetic permeability and the dielectric constant, the effective refractive index may also be improved. Such improvement of the effective refractive index can reduce the thickness of the absorbent required when the soft magnetic flake composite is used as a microwave absorber. That is, when the microwave absorbent in the form of a film is used, as the effective refractive index increases, the thickness of the absorber film having the maximum microwave absorption capacity may be reduced. Therefore, when the soft magnetic flake composite according to an embodiment of the present application is used as a microwave absorbing film material, microwave absorption is possible at a thinner thickness than the conventional soft magnetic flake composite.

In one embodiment of the present application, the thickness of the soft magnetic flake composite may be about 0.1 μm to about 5 cm, but may not be limited thereto. For example, the thickness of the soft magnetic flake composite is about 0.1 μm to about 5 cm, about 0.1 μm to about 4 cm, about 0.1 μm to about 3 cm, about 0.1 μm to about 2 cm, about 0.1 μm to about 1 cm, about 0.1 μm to about 8 mm, about 0.1 μm to about 6 mm, about 0.1 μm to about 5 mm, about 0.1 μm to about 4 mm, about 0.1 μm to about 2 mm, about 0.1 μm to about 1 mm, about 0.1 μm to about 0.5 mm, about 0.1 μm to about 100 μm, about 0.1 μm to about 50 μm, about 0.1 μm to about 10 μm, about 0.1 μm to about 5 μm, about 0.1 μm to about 1 μm, about 1 μm to about 5 cm, about 1 μm to about 4 cm, about 1 μm to about 3 cm, about 1 μm to about 2 cm, about 1 μm to about 1 cm, about 1 μm to about 8 mm, about 1 μm to about 6 mm, about 1 μm to about 5 mm, about 1 μm to about 4 mm, about 1 μm to about 2 mm, about 1 μm to about 1 mm, about 1 μm to about 0.5 mm, about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 1 μm to about 10 μm, about 1 μm to about 5 μm, about 5 μm to about 5 cm, about 5 μm to about 4 cm, about 5 μm to about 3 cm, about 5 μm to about 2 cm, about 5 μm to about 1 cm, about 5 μm to about 8 mm, about 5 μm to about 6 mm, about 5 μm to about 5 mm, about 5 μm to about 4 mm, about 5 μm to about 2 mm, about 5 μm to about 1 mm, about 5 μm to about 0.5 mm, about 5 μm to about 100 μm, about 5 μm to about 50 μm, about 5 μm to about 10 μm, about 10 μm to about 5 cm, about 10 μm to about 4 cm, about 10 μm to about 3 cm, about 10 μm to about 2 cm, about 10 μm to about 1 cm, about 10 μm to about 8 mm, about 10 μm to about 6 mm, about 10 μm to about 5 mm, about 10 μm to about 4 mm, about 10 μm to about 2 mm, about 10 μm to about 1 mm, about 10 μm to about 0.5 mm, about 10 μm to about 100 μm, about 10 μm to about 50 μm, about 50 μm to about 5 cm, about 50 μm to about 4 cm, about 50 μm to about 3 cm, about 50 μm to about 2 cm, about 50 μm to about 1 cm, about 50 μm to about 8 mm, about 50 μm to about 6 mm, about 50 μm to about 5 mm, about 50 μm to about 4 mm, about 50 μm to about 2 mm, about 50 μm to about 1 mm, about 50 μm to about 0.5 mm, about 50 μm to about 100 μm, about 100 μm to about 5 cm, about 100 μm to about 4 cm, about 100 μm to about 3 cm, about 100 μm to about 2 cm, about 100 μm to about 1 cm, about 100 μm to about 8 mm, about 100 μm to about 6 mm, about 100 μm to about 5 mm, about 100 μm to about 4 mm, about 100 μm to about 2 mm, about 100 μm to about 1 mm, about 100 μm to about 0.5 mm, about 0.5 mm to about 5 cm, about 0.5 mm to about 4 cm, about 0.5 mm to about 3 cm, about 0.5 mm to about 2 cm, about 0.5 mm to about 1 cm, about 0.5 mm to about 8 mm, about 0.5 mm to about 6 mm, about 0.5 mm to about 5 mm, about 0.5 mm to about 4 mm, about 0.5 mm to about 2 mm, about 0.5 mm to about 1 mm, about 1 mm to about 5 cm, about 1 mm to about 4 cm, about 1 mm to about 3 cm, about 1 mm to about 2 cm; about 1 mm to about 1 cm, about 1 mm to about 8 mm, about 1 mm to about 6 mm, about 1 mm to about 5 mm, about 1 mm to about 4 mm, about 1 mm to about 2 mm, about 2 mm to about 5 cm, about 2 mm to about 4 cm, about 2 mm to about 3 cm, about 2 mm to about 2 cm, about 2 mm to about 1 cm, about 2 mm to about 8 mm, about 2 mm to about 6 mm, about 2 mm to about 5 mm, about 2 mm to about 4 mm, about 4 mm to about 5 cm, about 4 mm to about 4 cm, about 4 mm to about 3 cm, about 4 mm to about 2 cm, about 4 mm to about 1 cm, about 4 mm to about 8 mm, about 4 mm to about 6 mm, about 4 mm to about 5 mm, about 5 mm to about 5 cm, about 5 mm to about 4 cm, about 5 mm to about 3 cm, about 5 mm to about 2 cm, about 5 mm to about 1 cm, about 5 mm to about 8 mm, about 5 mm to about 6 mm, about 6 mm to about 5 cm, about 6 mm to about 4 cm, about 6 mm to about 3 cm, about 6 mm to about 2 cm, about 6 mm to about 1 cm, about 6 mm to about 8 mm, about 8 mm to about 5 cm, about 8 mm to about 4 cm, about 8 mm to about 3 cm, about 8 mm to about 2 cm, about 8 mm to about 1 cm, about 1 cm to about 5 cm, about 1 cm to about 4 cm, about 1 cm to about 3 cm, about 1 cm to about 2 cm, about 2 cm to about 5 cm, about 2 cm to about 4 cm, about 2 cm to about 3 cm, about 3 cm to about 5 cm, about 3 cm to about 4 cm, Or it may be about 4 cm to about 5 cm, but may not be limited thereto.

In one embodiment of the present application, the soft magnetic flake composite may have a microwave absorption capacity of about -10 dB or more with a return loss, but may not be limited thereto. For example, the soft magnetic flake composite has a microwave absorption capacity of about -10 dB or greater, about -20 dB or greater, about -30 dB or greater, about -40 dB or greater, about -50 dB or greater, or -60 dB or greater. may have, but may not be limited thereto.

A second aspect of the present disclosure includes: (a) pulverizing a dielectric particle precursor mixture and then heat-treating to prepare dielectric particles; and (b) performing a heat press on the mixture prepared by mixing the soft magnetic flakes and the dielectric particles in a polymer matrix to obtain a soft magnetic flake composite. A method for producing a soft magnetic flake composite according to the first aspect, to provide.

Although a detailed description of overlapping parts with the first aspect of the present application is omitted, the contents described for the first aspect of the present application may be equally applied even if the description thereof is omitted in the second aspect of the present application.

In one embodiment of the present application, the polymer matrix is not particularly limited, but polyurethane (polyurethane; PU), paraffin wax, polydimethylsiloxane (PDMS), polyurethane acrylate (polyurethaneacrylate; PUA) and epoxy resin ( epoxy resin), but may not be limited thereto. In one embodiment of the present application, the polymer matrix may be polyurethane.

In one embodiment of the present application, the manufacturing method of the soft magnetic flake composite may be performed by a dry process.

In one embodiment of the present application, in (a), the heat treatment may be performed under an inert gas atmosphere, but may not be limited thereto. For example, the inert gas may be He, Ne, or Ar, but may not be limited thereto. Here, the inert gas atmosphere may be adjusted to generate oxygen vacancies in the dielectric particles, but may not be limited thereto.

In one embodiment of the present application, in (b), the shape of the soft magnetic flake composite may be determined according to the shape of the mold supporting the mixture. For example, according to the shape of the mold, the soft magnetic flake composite according to the embodiment of the present application can be prepared in an intended shape such as a film, a sheet, a toroidal, a sphere, or a hexahedron,

A third aspect of the present disclosure provides a device comprising the soft magnetic flake composite according to the first aspect.

Although detailed descriptions of parts overlapping with the first and second aspects of the present application are omitted, the descriptions of the first and second aspects of the present application are equally applicable even if the description is omitted in the third aspect of the present application. can

In one embodiment of the present application, the soft magnetic flake composite in the device may be to perform a microwave absorption function.

In one embodiment of the present application, the soft magnetic flake composite may be used without limitation in devices requiring a microwave absorption function. For example, the device may be used in military fields, buildings (exterior and interior materials), IT infrastructure construction, radio dark rooms, electronic products and communication equipment, or RFID (radio-frequency identification) for logistics, but is not limited thereto it may not be In addition, the device may be an electric heating device, an electric power device, a digital technology application device, a broadcast receiver, a high frequency device, or a small digital home appliance, but may not be limited thereto.

Hereinafter, the present application will be described in more detail using examples, but the following examples are only illustrative to help the understanding of the present application, and the content of the present application is not limited to the following examples.

[Example]

1. Substances and manufacturing methods

(1) Preparation of BTO particles

BTO particles were prepared by molten salt synthesis (MSS) method. BaC ₂ O ₄ (Alfa Aesar) was mixed with TiO ₂ (Alfa Aesar), NaCl (Daejung) and KCl (Daejung) in a molar ratio of 3:3:37.5:37.5. The mixture was pulverized using a mortar and mortar, annealed in an Ar atmosphere at 950° C. for 5 hours using a tube furnace, and then cooled to room temperature over 12 hours. The Ar gas flow rate was adjusted to create oxygen defects in the BTO particles. The cooled product was collected and washed several times with distilled water until free chloride ions were no longer detected by silver nitrate titration. After drying at 60° C. overnight, the particles were annealed at 550° C. with a flow of Ar gas of 200 sccm for 5 hours and cooled to room temperature over 6 hours. On the other hand, the reduced particles were heat-treated in air at the same temperature and duration as above, to prepare white BTO particles.

(2) Preparation of FeSiAl-BTO particle composite

FeSiAl flake powder and DBTO particles were mixed in polyurethane (PU) dissolved in toluene using a paste mixer. After drying in an oven for 10 minutes, the mixture was pressed in an annular (doughnut) or film-shaped mold using a hot press machine at 100° C. for 30 minutes at a pressure of 4 MPa. Composite sets with FeSiAl:DBTO mass content of 60 wt%: 10 wt%, 40 wt%: 30 wt%, 30 wt%: 40 wt% and 10 wt%: 60 wt% were prepared. The FeSiAl-WBTO composite was prepared in the same way, in which WBTO particles were substituted for DBTO particles.

2. Characterization

(1) Characterization of FeSiAl-BTO

The size, orientation and compression of FeSiAl-BTO particles were analyzed by field emission scanning electron microscopy (FESEM, JOEL, JSM-6700F) at an operating voltage of 15 kV. To prepare the cross-section composites for SEM analysis, an automatic grinder (MetPrep4/PH-6) was used. The relative complex permittivity and permeability were obtained with an impedance analyzer (E4991A) using a DC power supply. For composite permittivity measurements, film samples were measured using a 16453A fixture, which uses a parallel plate method in which a film is sandwiched between two electrodes to form a capacitor. For complex permeability measurements, measurements were made with toroidal samples using a 16454A fixture that uses a one-turn mechanism to eliminate magnetic flux leakage.

(2) Calculation of complex wavelength impedance and return loss

The composite wavelength impedance and return loss of FeSiAl-BTO particles were calculated using the following equations:

Z _in = Z ₀ (με) ^1/2 tanh[i(2πfd/c)(με) ^1/2 ] (One)

RL(dB) = 20 log│(Z _in - Z _o )/(Z _in + Z ₀ )│ (2)

where ε and μ are the relative permittivity and permeability of the BTO particles, respectively, f is the frequency, d is the thickness of the composite, c is the speed of light, Z ₀ is the impedance of free space, Z _in is the input impedance of the absorber, RL ( dB) is the return loss.

(3) Measurement using a vibrating sample magnetometer

The magnetic properties were characterized with a vibrating sample magnetometer (VSM; Microsense). After the film composite sample prepared on the Si/SiO _x substrate was loaded into the sample holder of the VSM, the magnetic moment was measured as a function of a DC magnetic field from -20 kOe to 20 kOe. The magnetic hysteresis loop was measured in the plane direction. The magnetic moment per volume (emu/cc) was calculated from the shape of the sample, i.e., the substrate area and the film thickness. The sensitivity of the VSM was pre-calibrated with a commercial Ni film kit. The linear background signal, a parasiutic effect from the substrate and holder, was removed.

3. Measurement and analysis

(1) Analysis of physical properties of FeSiAl flakes and dielectric loss-type BTO particles

A (70 wt%-x)FeSiAl-xBaTiO ₃ particle composite was prepared by a simple mixing and hot pressing process. FeSiAl flakes in powder form were purchased from JMC Corporation (Fig. 2a inset). SEM analysis shows that the flakes have lateral dimensions between 10 microns and 100 microns ( FIG. 2A ). Fig. 2b shows the characteristic XRD peak of FeSiAl (mass ratio of 40 wt%) mixed in polyurethane resin, indicating that FeSiAl is highly crystalline and cubic. BaTiO ₃ (BTO) particles were synthesized using a previously reported method. The prepared white BTO (WBTO) particles were chemically reduced to black BTO (DBTO) particles using Ar gas to increase the dielectric constant by introducing oxygen deprivation. Both DBTO and WBTO particles share the same average particle size of 800 nm to 1 micron as observed by SEM (Fig. 2c). XRD analysis of DBTO particles indicates that the crystalline phase is tetragonal, confirming ferroelectricity (Fig. 2d).

The composite manufacturing process is shown in Figure 2e. WBTO or DBTO particles were mixed with FeSiAl flakes in a polyurethane (PU) resin in a series of different mass ratios to prepare mixtures. The mass ratio of total fillers (BTO particles and FeSiAl flakes) was fixed at 70 wt% and PU was used for the remaining 30 wt%. A PU mass fraction of less than 30 wt % resulted in dissociation of the complex. The mixture was heated at 4 MPa and 100° C. for 30 minutes in the form of donut-shaped pellets (inner and outer diameters of 3 mm and 7 mm and thickness of 2.8 mm, respectively) or films (1.2 x 1.2 x 1 mm ³ ). became Four (70 wt%-x)FeSiAl-xBaTiO ₃ (x = 10 wt%, 30 wt%, 40 wt% and 60 wt%) composites were prepared. For comparison with the composite without BTO particles, four reference samples composed of FeSiAl flakes with the same FeSiAl mass content as the corresponding FeSiAl-BTO composite were prepared. The four reference samples consisted of 40 wt%, 60 wt%, 70 wt% and 90 wt% PU, respectively, with 60 wt%, 40 wt%, 30 wt% and 10 wt% of FeSiAl, respectively. Unless otherwise noted, the mass ratio of the PU matrix is omitted from the description of the composite for simplicity. Before heat pressing, it was assumed that the FeSiAl flakes and BTO particles of the mixture were randomly distributed without directionality as shown in the left inset of Fig. 2e. However, applying heat and high pressure to the mixture in the mold aligns the flakes so that the flake surface is approximately flush with the top composite surface as shown in the right inset of FIG. 2E . Relative intensity XRD analysis of the crystalline peaks can provide evidence of flake alignment, as seen in FeSi flakes thermocompressed in a polymer matrix. Similar to this previous report, we found that the relative intensity of the (200) peak of FeSiAl increased and the (110) peak decreased for the thermocompression-bonded sample, as shown in Fig. 2b. This change in relative peak intensity is due to mechanical deformation, which induces deformation along a direction perpendicular to the flake surface, and creates a larger population of (100) textures. Cross-sectional SEM analysis of the composites described below confirmed a high degree of flake alignment. A (200)-(110) peak intensity ratio was used to monitor and ensure consistent flake alignment between different composite and reference samples. (Fig. 3).

(2) Cross-sectional analysis and X-ray diffractometer analysis of FeSiAl flake-BTO particle composites

To understand the microstructural differences between the FeSiAl composites with and without DBTO particles (thus leading to different EM properties), cross-sectional SEM images were compared as shown in FIG. 4 . A pair of reference and composite samples with FeSiAl mass ratios of 60 wt% and 40 wt% are shown in Figures 4a-b and 4c-d, respectively. It can be seen that in all cases, the flakes tend to align along the horizontal direction, consistent with the (200) to (110) XRD peak intensity ratio.

For adjacent flakes that are slightly vertically apart, two flakes can come into contact if one of the flakes is slightly tilted towards the other. This can be seen in Figures 4a and 4c, where two instances of flakes can be found vertically spaced at the edges with near or complete contact. Since the physical contact between adjacent flakes can broaden the eddy current path (Fig. 4e), it has a great impact on the magnetic properties of the composite, which opposes the applied magnetic field and reduces the effective permeability.

The present inventors have found that simple mixing of dielectric particles can be an effective route to block the eddy current path and improve the permeability. The inclusion of dielectric particles in the composite allows the particles to randomly intercalate between vertically adjacent flakes, preventing the flakes from collapsing into each other under pressure applied during composite fabrication (see FIG. 4f ). Figures 4b and 4d show that adding DBTO particles to the composite makes vertically adjacent flakes less likely to contact each other because the particles are positioned between them. This geometric effect restricts the eddy current loop to isolated flakes, enhancing the effective permeability of the composite (Fig. 4f). An increase in the BTO content at the consumption of the FeSiAl content leads to an increase in the possibility of flake segregation, as can be seen in FIGS. 4b and 4d (where the higher concentration of DBTO particles is x = 30 compared to x = 10 wt% composites) between the vertically stacked flakes for the wt% composite). The spatial distribution of flakes and particles is similar in the composites with WBTO as DBTO and WBTO particles share the same size distribution. The SEM image of Fig. 4 only provides a two-dimensional cross-sectional view of the three-dimensional configuration. Flakes can tilt in the cross-section direction, but also in a plane orthogonal to both the cross-section and the top surface that are hidden from view. Therefore, it is assumed that the overall spatial extent of flake separation by BTO particles is broader given the overall three-dimensional orientation of the flakes. The difference in EM response between the composite and the reference sample is not expected to be due to the change in flake density, as low magnification SEM images of the composite material with and without DBTO particles show no appreciable difference in compression.

It is important to note that the FeSiAl-DBTO composite experiences more internal stress than the corresponding FeSiAl reference sample. These stresses can affect the magnetic properties of iron-rich alloys because of the susceptibility of ferromagnetic exchange interactions to interatomic spacing. The DBTO particles of the composite occupy more volume than the PU matrix of the same mass of the reference. Because the composite and reference are heat pressed to the same sample dimensions as the reference, the additional volume of DBTO particles causes the FeSiAl flakes of the composite to be more stressed than the reference flakes. Although it is difficult to observe evidence of increased mechanical strain in the composite material in SEM and XRD analysis due to the large statistical deviation of the flake thickness observed by cross-sectional SEM and the overlap of FeSiAl and DBTO XRD peaks, DBTO with a larger mass ratio compared to PU and DBTO particles indicates that an additional force is applied to the FeSiAl flakes with

(3) Analysis of Saturated Magnetic Flux Density of FeSiAl Flake-BTO Particle Composite Set

To test this hypothesis, magnetic hysteresis curves of the composite and reference films were obtained for x = 10 wt % and 30 wt % in vibratory sample magnetometer (VSM) measurements (see Supplementary Materials) as shown in FIG. 5 . Due to the addition of DBTO particles, the saturation magnetization (MS) increased from ∼20.5 emu/cc to ∼31.7 emu/cc for x = 10 wt % and from 13.1 emu/cc to 20.9 emu/cc for x = 30 wt %. As a result, it can be seen that 1.6 and 1.5 were improved, respectively. Because VSM measures static properties, these results cannot arise from AC effects such as changes in eddy currents. Specifically, Figure 5a is a result of comparing the saturation magnetic flux density of the FeSiAl 60 wt% composite and FeSiAl 60 wt% + BTO 10 wt% composite. Only 10 wt% of DBTO and WBTO particles having a saturation magnetic flux density of almost 0 were added, and it can be seen that the saturation magnetic flux density of the existing 60 wt% FeSiAl is increased by 1.6 times. In addition, referring to FIG. 5b, it was confirmed that the saturation magnetic flux density was increased by 1.5 in the FeSiAl 40 wt% + BTO 30 wt% composite compared to the FeSiAl 40 wt% composite.

The magnetic hysteresis curves of the FeSiAl-WBTO samples were also measured and displayed in Fig. 5 for comparison, showing that no type of magnetic interaction with free electron spins associated with oxygen vacancies in DBTO results in enhanced MS. Composites containing the same mass of DBTO and WBTO particles generate a similar level of saturation magnetization, confirming that mechanical stress is the dominant effect. It is known that the increased saturation magnetization is conducive to the dynamic magnetic properties, and the high-frequency permeability of the composite is improved compared to the reference sample.

These results contrast with the previous report on FeSiAl/BTO/Nd ₂ Fe ₁₄ B, in which the addition of BTO particles showed a decrease in saturation magnetization, presumably due to the lack of applied stress when preparing the composite.

(4) Analysis of Permeability and Permittivity of FeSiAl Flake-BTO Particle Composite Set

By measuring the composite and reference film with an impedance analyzer (E4991A), the improved permeability and dielectric constant of the FeSiAl composite due to the addition of DBTO particles were confirmed. Flake alignment provides the anisotropy and effective permittivity of samples composed of in-plane and out-of-plane components to the composite. In this specification, the EM wave is generally incident on the top surface of the composite, so the in-plane components of permittivity and permeability were measured and used for all subsequent analyses.

6a shows the composite permeability as a function of frequency for the FeSiAl-DBTO composites having x = 10 wt%, 30 wt%, 40 wt% and 60 wt%, in which FeSiAl flakes, DBTO, and WBTO particles are mixed in a certain ratio. It is the result of comparative analysis of the real and imaginary parts of the permeability of the set with the FeSiAl flake composite in the 1-1000 MHz band. For comparison, the composite permeability of the corresponding reference sample is indicated by the black line. It can be seen that when a small amount of BTO particles are added to FeSiAl flakes, both the permeability real and imaginary parts increase in the MHz band than the permeability of the existing FeSiAl flakes. For all FeSiAl-DBTO composites, the permeability is higher than the reference for the measured frequency, and it can be confirmed that the addition of DBTO particles can improve the permeability by suppressing eddy currents and increasing saturation magnetization. In the sample with reduced FeSiAl loading, the absolute value of permeability decreased, while the improvement of permeability increased compared to the reference. The enhancement coefficients of μ′, the actual fraction of permeability at 1 MHz, were 1.1, 1.5, 1.6 and 1.7 for x = 10 wt%, 30 wt%, 40 wt% and 60 wt%, respectively, which are the composite SEM of Figs. 4b and 4d. As can be seen in the image, it is suggested that the higher loading of DBTO particles improved the permeability. Similar to the saturation magnetization results, the permeability improvement of the FeSiAl-DBTO and FeSiAl-WBTO composites was similar. This confirms that the improved permeability is determined by the geometry because the DBTO and WBTO particle sets share the same size distribution, and the effect can be extended to other non-magnetic particles with similar size distribution, thus making the material less magnetic. can be used to achieve equivalent magnetic properties.

In addition, the dielectric effect of BTO particles on the composite was evaluated. The composite permittivity of the four complexes was measured using the same impedance analyzer (E4991A) as previously described. Figure 6b is the result of comparative analysis of the real and imaginary parts of the dielectric constant of the composite set in which FeSiAl flakes, DBTO, and WBTO particles are mixed at a certain ratio with the FeSiAl flake composite in the 1-1000 MHz band, where the dielectric constant of the composite with the introduction of BTO It can be seen that the real part ε' and the imaginary part ε” of are higher than the permittivity of the FeSiAl reference sample corresponding to all mass ratios. This increase is due to the high intrinsic complex permittivity of BTO particles. The comparison between DBTO and WBTO particles in Fig. 6b also shows that oxygen starvation engineering of BTO can further tune the complex permittivity. The enhancement coefficients of ε' for DBTO (WBTO) composites with x = 10 wt%, 30 wt%, 40 wt% and 60 wt% at 1 MHz were 1.4 (1.4), 1.8 (1.7), 2.8 (2.5) and 3.6 ( 3.2), and compared with each reference. It can be seen that the improvement coefficient of the DBTO composite is consistently higher than that of the WBTO composite. This can provide important freedom for controlling the oxygen vacancies of the BTO particles to tune the permittivity, which can be useful for balancing the refractive index and impedance properties.

(5) Analysis of effective refractive index of FeSiAl flake-BTO particle composite set

)을 표시하였다. 굴절률은 1MHz 이상의 광대 한 주파수 범위에서 비교적 일정하게 유지되고 투과성의 급격한 감소로 인해 1GHz에 도달하기 전에 급격히 떨어진다. 60 wt%, 40 wt%, 30 wt% 및 10 wt%의 FeSiAl이 포함된 레퍼런스 샘플의 경우 초기 굴절률 (1MHz)은 ~ 20, ~ 9.4, ~ 7 및 ~ 3.4이다. DBTO가 x = 10 wt%, 30 wt%, 40 wt%, 및 60 wt%로 추가되면 초기 굴절률은 1.3, 1.7, 2 및 2.4의 향상 계수에 해당하는 ~25, ~16, ~14 및 ~8.2로 향상된다. 도 6에 표시된 투자율 및 유전율 플롯에서 예상되어진대로, 감소된 FeSiAl 부하는 더 작은 절대 굴절률을 생성하지만, 상응하는 레퍼런스의 굴절률에 비해 향상이 증가한다. 결론적으로, FeSiAl 플레이크에 소량의 BTO 입자들을 첨가하여 복합체의 유효 굴절률이 모두 기존의 FeSiAl 플레이크 복합체 유효 굴절률보다 MHz 대역에서 상승하는 것을 알 수 있다.The simultaneous increase of magnetic permeability and dielectric constant with the addition of DBTO particles can be used to realize an effective intermediate with substantially higher refractive index. In Fig. 7, up to 1 GHz, we show the refractive index of all four composites.

) is indicated. The refractive index remains relatively constant over a broad frequency range above 1 MHz and drops sharply before reaching 1 GHz due to a sharp decrease in transmittance. For reference samples containing 60 wt %, 40 wt %, 30 wt % and 10 wt % of FeSiAl, the initial refractive indices (1 MHz) are ∼20, ∼9.4, ∼7 and ∼3.4. When DBTO is added at x = 10 wt%, 30 wt%, 40 wt%, and 60 wt%, the initial refractive indices are ∼25, ∼16, ∼14, and ∼8.2 corresponding to enhancement coefficients of 1.3, 1.7, 2, and 2.4. is improved with As expected from the permeability and permittivity plots shown in Figure 6, the reduced FeSiAl loading produces a smaller absolute refractive index, but an increase in improvement over the corresponding reference refractive index. In conclusion, it can be seen that by adding a small amount of BTO particles to FeSiAl flakes, the effective refractive index of the composite all increases in the MHz band than the effective refractive index of the conventional FeSiAl flake composite.

(6) Analysis of the microwave absorption capacity of the FeSiAl flake-BTO particle composite set

=1 및

=0인 경우에 해당하는 파동 임피던스가 공기와 일치할 때 발생한다. 도 8b로부터, 도 6a에 나타난 반사 손실 최소값에 해당하는 두께와 주파수에서 두 조건이 동시에 충족됨을 알 수 있다. 단일 지점에서 두 조건의 교차점은 자기 손실과 높은 투자율의 결과이며, 이것은 파동 임피던스의 상 이동을 도입한다. 파동 임피던스 매칭 조건에 대한 보다 명확한 설명을 위해, 도 8c는 임피던스 정합 복합 필름 두께 7.6 mm (왼쪽 패널)에서 반사 손실과 복합 파동 임피던스를 보여준다. 반사 손실 최소값은

=1 및

=0 충족되는 조건에서 만족되며, 반면 레퍼런스 샘플의 경우 복합 파동 임피던스는 동일한 두께(오른쪽 패널)에서 두 조건을 모두 놓친다는 것을 알 수 있으며, 이것은 상당한 반사 손실이 없는 결과를 초래한다.The main reason for achieving the improved refractive index is the reduced absorber film thickness. We calculated the return loss of a representative composite and corresponding reference sample of x = 30 wt % from the measured composite permittivity and permeability. Figure 8a shows the return loss of two films calculated as a function of thickness and frequency. A comparison of the other three sets (x = 10 wt %, 40 wt %, 60 wt %) is shown in FIG. 9 . It can be seen in Figure 8a that the thickness for maximum absorption is dramatically reduced with DBTO particles (left panel) compared to the absence of particles (right panel). The maximum absorption occurs at 13.5 mm and 985 MHz for the reference sample and at 7.6 mm and 885 MHz for the composite with DBTO particles, which corresponds to a 1.8-fold improvement in the thickness-to-wavelength ratio. This enhancement ratio is quite consistent with the refractive index average enhancement ratio (1.7) between 870 MHz and 900 MHz. As expected from the higher dielectric constant of DBTO particles compared to WBTO particles, the fully absorbent composite with DBTO particles was thinner than the composite using WBTO particles as shown in FIG. 9 . This indicates that oxygen starvation engineering of the BTO particles can further fine-tune the absorber film thickness. The composites herein produce perfect absorption (return loss -60 dB) that is limited to thickness and frequency. Outside of this thickness, the return loss decreases sharply, as shown in Figure 10, indicating that the film develops exceptional thickness sensitivity. In order to understand the separation (discrete) of the return loss, the complex wave impedance matching condition as a function of thickness and frequency is presented in Fig. 6b. the maximum absorption

=1 and

Occurs when the wave impedance corresponding to the case of =0 coincides with air. From FIG. 8B , it can be seen that both conditions are simultaneously satisfied at the thickness and frequency corresponding to the minimum return loss value shown in FIG. 6A . The intersection of the two conditions at a single point results in magnetic losses and high permeability, which introduces a phase shift in the wave impedance. For a clearer explanation of the wave impedance matching condition, Fig. 8c shows the return loss and the complex wave impedance at an impedance matching composite film thickness of 7.6 mm (left panel). The minimum return loss is

=1 and

It can be seen that the condition where =0 is satisfied, whereas for the reference sample the complex wave impedance misses both conditions at the same thickness (right panel), which results in no significant return loss.

(7) Analysis of Saturated Magnetic Flux Density of FeSiAl Flake-BTO Particle Composite Set

It was further analyzed whether the dry process method used in this experiment could be applied to other materials with similar properties to FeSiAl and BTO particles. FeSiAl flakes have different magnetic properties depending on the specific gravity of each chemical element. For further analysis, FeSiAl flakes with different chemical element specific gravity were used in this experiment, and BTO particles, which act as dielectrics and insulators, were analyzed by replacing them with TiO ₂ particles.

11a and 11b are results of measuring the saturation magnetic flux density of FeSiAl + TiO ₂ composites. 11a is a result of comparing the saturation magnetic flux density of the FeSiAl 60 wt% composite and the FeSiAl 60 wt% + TiO ₂ 10 wt% composite. Only 10 wt% of TiO ₂ particles having a saturation magnetic flux density of almost 0 were added, and this result also showed a slight increase compared to the saturation magnetic flux density of the existing 60 wt% FeSiAl. In addition, according to FIG. 11b, it was confirmed that the saturation magnetic flux density was increased by 40% in the FeSiAl 40 wt% + TiO ₂ 30 wt% composite compared to the FeSiAl 40 wt% composite. Therefore, the assumption of this experiment that the existing FeSiAl magnetic properties can be further reinforced by suppressing eddy current loss by adding small amounts of particles acting as dielectrics and insulators to FeSiAl flakes is limited to BTO and specific FeSiAl flakes through the dry process. It has been confirmed that it can be applied without

4. Conclusion

The present inventors have found that when ferroelectric BTO particles are mixed into the soft magnetic FeSiAl flake composite, the magnetic permeability and the dielectric constant of the composite can be simultaneously improved to reduce the thickness of the absorbent film and increase the thickness sensitivity. Although the improvement in permittivity is easy to understand as it derives from the ferroelectric contribution of the BTO particles, the interesting effect of the increase in permeability by adding nonmagnetic BTO particles was found to be due to the intercalation of the particles between adjacent FeSiAl flakes, preventing the flakes from contacting. . This arrangement breaks the eddy current path and applies increased stress to the flakes which increases the saturation magnetization. The above two effects improve the effective permeability compared to the case without BTO particles. Oxygen defect engineering can further tune the dielectric constant to provide a convenient degree of freedom to balance the characteristic impedance and refractive index of the composite. When the magnetic permeability and the dielectric constant are increased simultaneously, the refractive index can be greatly improved and the film thickness can be reduced. As a result of adding 30 wt% DBTO particles, it was found that the thickness of the composite could be reduced by almost 2 times. We also show that the wave impedance matching condition localizes the absorption to a fixed thickness and frequency, so that very large return loss values (~60 dB) are achieved. Since BTO is an inexpensive ferroelectric material and the permeability is improved by simple mixing of BTO particles, these results suggest interesting possibilities for the development of high-performance EM wavelength-absorbing films with significantly reduced thickness compared to their dielectric or magnetic counterparts.

The above description of the present application is for illustration, and those of ordinary skill in the art to which the present application pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and likewise components described as distributed may also be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims, and their equivalents should be construed as being included in the scope of the present application. .

Claims (16)

A soft magnetic flake composite comprising soft magnetic flakes and dielectric particles, comprising:
The soft magnetic flakes are arranged in a stacked structure,
Dielectric particles are included between the soft magnetic flakes,
Physical stress is applied to the surface of the soft magnetic flake by the dielectric particles, and the atomic structure deformation of the soft magnetic flake appears,
Soft magnetic flake composite.
delete The method of claim 1,
The soft magnetic flakes include at least one selected from FeAlSi, Fe-Si alloy, Ni-Fe alloy, and MO _x ·Fe ₂ O ₃ ,
Wherein M is Ni, Mn or Zn,
0≤x<3,
Soft magnetic flake composite.
The method of claim 1,
The dielectric particles are BaTiO _3-y , TiO _2-z , Si, Ge, Sn, SiC, S ₈ , Se, Te, BN, BP, BAs, ZnO, ZnSe, ZnS, ZnTe, CuCl, Cu ₂ S, PbSe , PbS, ObTe, SnS, SnS ₂ , SnTe, B ₁₂ As ₂ , AlN, AlP, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, CdS, CdSe, CdTe, InGaP, InGaN, InN, InP, InAs , InSb, PbSeTe, Tl ₂ SnTe ₅ , Tl ₂ GeTe ₅ , Bi ₂ Te ₃ , Cd ₃ P ₂ , Cd ₃ As ₂ , Cd ₃ Sb ₂ , ZnsP ₂ , Zn ₃ As ₂ , Zn ₃ Sb ₂ , Cu ₂ O, CuO, UO ₂ , UO ₃ , Bi ₂ O ₃ , SnO ₂ , SrTiO 3 , LiNbO ₃ , La ₂ CuO ₄ , PbI ₂ , MoS ₂ , VO ₂ , V ₂ O ₃ , _GaSe , Bi ₂ S ₃ , NiO, CuInSe ₂ , Ag ₂ S, FeS ₂ , Cu ₂ ZnSnS ₄ , CuZnSbS, Cu ₂ SnS ₃ , Si _1-x Ge _x , Si _1-x Sn _x , AlxGa _1-x As, InxGa _1-x As, In _x Ga _1-x P, Al _x In _1-x As, Al _x In _1-x Sb, GaAsN, GaAsP, GaAsSb, AlGaN, AlGaP, InGaN, InAsSb, InGaSb, AlGaInP, AlGaAsP, IGaAsP, InGaAsSb, InAsSbP, Containing at least one material selected from AlInAsP, AlGaAsN, InGaAsN, InAsAsN, GaAsSbN, GaInNAsSb, GaInAsSbP, CdZnTe, HgCdTe, HgZnTe, HgZnSe, and Cu(In,Ga)Se ₂ ,
0≤y<3, and 0≤z<2,
Soft magnetic flake composite.
5. The method of claim 4,
wherein the dielectric particles are axially deoxygenated.
The method of claim 1,
The soft magnetic flakes and the dielectric particles have a weight ratio of 8: 1 to 1: 8, the soft magnetic flake composite.
delete The method of claim 1,
The soft magnetic flake composite will absorb microwaves, the soft magnetic flake composite.
The method of claim 1,
The soft magnetic flake composite has a thickness of 0.1 μm to 5 cm.
The method of claim 1,
The soft magnetic flake composite will have a microwave absorption capacity of less than -10 dB of return loss, the soft magnetic flake composite.
(a) pulverizing the dielectric particle precursor mixture and then heat-treating to prepare dielectric particles; and
(b) performing a heat press on the mixture prepared by mixing the soft magnetic flakes and the dielectric particles in a polymer matrix to obtain a soft magnetic flake composite
A method for producing a soft magnetic flake composite according to any one of claims 1 to 6, and claims 8 to 10, comprising:
The soft magnetic flakes are arranged in a stacked structure,
Dielectric particles are included between the soft magnetic flakes,
By adding the dielectric particles between the soft magnetic flakes and heat pressing, a physical stress is applied to the surface of the soft magnetic flakes by the dielectric particles, and deformation of the atomic structure of the soft magnetic flakes appears. A method for preparing the composite.
12. The method of claim 11,
A method for producing a soft magnetic flake composite, which is performed by a dry process.
12. The method of claim 11,
In (a), the heat treatment is performed under an inert gas atmosphere, the method for producing a soft magnetic flake composite.
12. The method of claim 11,
In (b), the shape of the soft magnetic flake composite is determined according to the shape of the mold supporting the mixture, the method for producing a soft magnetic flake composite.
11. A device comprising the soft magnetic flake composite according to any one of claims 1 and 3 to 6 and 8 to 10.
16. The method of claim 15,
wherein the soft magnetic flake composite in the device performs a microwave absorbing function.

Images